FIGS. 8(a) to 8(c) show a structure of connection between a terminal and an electric wire described in Patent Reference 1.
As shown in FIGS. 8(a) and 8(b, in this structure of connection between the terminal and the electric wire, a metallic cap 230 with the size in which the range from a conductor (mainly including a twisted wire obtained by twisting many strands together) Wa exposed by removing an insulating coating Wb to the portion having the insulating coating Wb is covered is first attached to the distal end of an electric wire W, and the insertion portion of the conductor Wa of the distal end of the electric wire W to which the cap 230 is attached is placed on a base plate part 221 of an electric wire connection part 212 formed in the back of a terminal 210. In that state, as shown in FIG. 8(c), a pair of conductor crimping pieces 222 upwardly extending in both lateral edges of the base plate part 221 is crimped and fixed so as to obtain a state in which the conductor Wa and the cap 230 make close contact with an upper surface of the base plate part 221 by inwardly bending the conductor crimping pieces 222 so as to wrap the conductor Wa and the cap 230.
In the cap 230, a portion 231 into which the outer periphery of the conductor Wa is fitted is formed in a tube shape with a small diameter, and an inlet side portion 232 into which the outer periphery of the insulating coating Wb is fitted is formed in a tube shape with a large diameter, and a gap between the conductor Wa and the cap 230 is filled with a waterproof filler (not shown). Also, an inner peripheral surface of the electric wire connection part 212 of the terminal 210 is provided with serrations 228 for increasing contact continuity between the cap 230 and the terminal 210.
The reason why the cap 230 is used herein is because electrolytic corrosion may occur when water adheres to a part of contact between different kinds of metals (that is, a press bond part) in the case where, for example, the conductor Wa of the electric wire W is made of aluminum or aluminum alloy and the terminal 210 is made of copper or copper alloy, and a material of the cap 230 is set in the same kind (copper or copper alloy) as a material of the terminal 210 in order to prevent such electrolytic corrosion from occurring. Also, a terminal made of aluminum or aluminum alloy can be used for an aluminum electric wire, but both of the terminal 210 and the cap 230 are made of copper or copper alloy for the reason why the terminal made of copper or copper alloy has an advantage over the terminal made of aluminum or aluminum alloy in strength. When the materials are selected thus, the cap 230 is made of metal different from that of the conductor Wa of the electric wire W (the former is made of copper or copper alloy and the latter is made of aluminum or aluminum alloy), but a gap between the conductor Wa and the cap 230 is filled with a filler (not shown), and water is prevented from entering the inside of the cap 230 and there is no fear of electrolytic corrosion.